NRRPT - National Registry of Radiation Protection Technicians Detection and Measurement Questions and Answers

Question 1

A radiation protection technologist is using a Geiger-Mueller (GM) survey meter in a high-count-rate field. The instrument reading appears to be erroneously low. Which of the following phenomena is the most likely cause for this inaccurate reading?

Accepted Answer

Dead time

Answer

At high count rates, a GM detector can experience 'dead time,' a period after an ionization event during which the detector is unable to register another event. [6, 7] If the rate of incoming radiation events is faster than the detector's recovery time, some events will not be counted, leading to an instrument reading that is lower than the actual radiation field.

Question 2

Which of the following detectors is best suited for accurately measuring the energy of gamma radiation and performing isotopic identification?

Accepted Answer

Sodium Iodide (NaI) scintillation detector

Answer

Sodium Iodide (NaI) scintillation detectors are highly efficient for gamma-ray detection. [18] The amount of light produced (scintillation) is proportional to the energy deposited by the gamma ray, allowing for energy spectrometry and the identification of specific radionuclides based on their characteristic gamma energies. [28]

Question 3

A technician needs to measure the dose from a low-energy beta source on the skin. Which type of detector would be most appropriate for this scenario?

Accepted Answer

A pancake-style Geiger-Mueller probe with a thin window

Answer

Low-energy beta particles have a very short range and are easily attenuated. A pancake GM probe with a thin mica window allows these low-energy betas to enter the sensitive gas volume of the detector to be counted. [6] Thick-walled detectors would shield the betas, and NaI detectors are primarily used for gamma detection.

Question 4

The operating principle of a thermoluminescent dosimeter (TLD) is based on which of the following phenomena?

Accepted Answer

Emission of light proportional to deposited energy upon heating

Answer

Thermoluminescent dosimeters (TLDs) work by trapping electrons in an excited state within a crystal lattice when exposed to ionizing radiation. When the crystal is heated, these electrons return to their ground state, releasing the stored energy as visible light. The amount of light emitted is proportional to the radiation dose received. [3, 25, 35]

Question 5

Which of the following describes the 'intrinsic efficiency' of a radiation detector?

Accepted Answer

The ratio of pulses produced to the number of particles striking the detector.

Answer

Intrinsic efficiency is defined as the ratio of the number of pulses produced by the detector to the number of radiation quanta (e.g., gamma rays) that are incident on the detector's sensitive volume. It represents the probability that a particle striking the detector will cause a recorded event. [14]

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

(NRRPT) National Registry of Radiation Protection Technicians Practice Test

NRRPT - National Registry of Radiation Protection Technicians Detection and Measurement Questions and Answers